The invention concerns a ring seal for apertures of multi-shell structures especially of underground operation.
The invention is related especially to ring seals in shaft and tunnel construction, as well as in sewer construction, where often a multi-shell structure is provided as an exterior construction of the underground cavity. The outside of the structure can thereby consist of the exposed rock wall or of a preliminary structure, for the most part realized with sprayed concrete. The interior shell of a structure of this kind, which forms the inner shell of the ring aperture, consists then, as a rule, of a static load-bearing structure in concrete or reinforced concrete, for which waterproof concrete (so-called WU-concrete) is a possibility. The ring seal concerned in this invention serves with the help of a hollow sealing element for the frontal sealing of the ring aperture, in order to stop the flow of either water or sludge from this aperture, or to fill up the circular space behind the frontal seal.
It is known how to construct the specific sealing element out of a self-enclosed ring with a circular cross-section as a so-called O-ring seal with an unending rubber tube, which has a filling from air or a fluid. O-ring seals of this kind are specially manufactured and designed for each individual case. They require a firm seat as the seal clamping fixture into which they are built. Such O-ring seals are technically expensive. Since they are applied to a specific ring aperture width and diameter, changes in the form of the ring have negative consequences of the sealing, possibly the ring aperture diameter and breadth differing from each other. Since one can seal only the concerned ring aperture with the ring seal designed for the individual installation case, but this is to be followed under the given relationships only with relatively great tolerances, a sufficient sealing of the ring aperture by using these O-ring seal causes considerable difficulty in some circumstances. In particular, differing internal diameters determined by the procedure, which might, for example, be made necessary by the thrusting technology or even by other reasons, can be sealed only with two sealing elements of the kind described, built in next to each other. Then, for reasons of space, there often result difficulties in the installation of these multiple sealing elements.
Beyond this, such sealing elements are not secure against leakage of their filling, which leads to the failure of the ring aperture seal, since the sealing pressure is lost. It is common to the described ring aperture seals that either they must be disposed of after the end of the work, or after the completion of the structure they form a so-called "soft spot" in the statics of the structure. With this it must also be considered that the known O-ring seals conditioned by the manner of construction resist only limited counter-pressures. With air-filled sealing elements the counter-pressures are, as a consequence of the air-pressure container regulation, limited to allowable values, which can easily be inadvertently surpassed in the finished structure underground.